[FFmpeg-devel] [PATCH]lavc/opus_rc: Case a const pointer to uint8_t *

[Carl Eugen Hoyos]

2018-12-17 21:35 GMT+01:00, Rostislav Pehlivanov <atomnuker at gmail.com>:
> On Mon, 17 Dec 2018 at 01:47, Carl Eugen Hoyos <ceffmpeg at gmail.com> wrote:
>
>> Hi!
>>
>> The Opus struct RawBitsContext is used in both the decoder and the
>> encoder.
>> The fact that *position is const avoids warnings in the decoder where
>> it points into the bitstream. The encoder writes into the same
>> pointer, attached cast silences the warning on targets where AV_WB32()
>> does not internally cast the qualifier away.
>>
>> It is also possible to use a union if anybody prefers this:
>> diff --git a/libavcodec/opus_rc.h b/libavcodec/opus_rc.h
>> index 627f832..baad4ce 100644
>> --- a/libavcodec/opus_rc.h
>> +++ b/libavcodec/opus_rc.h
>> @@ -37,9 +37,19 @@ typedef struct RawBitsContext {
>>      uint32_t cacheval;
>>  } RawBitsContext;
>>
>> +typedef struct RawBitsEncContext {
>> +    uint8_t *position;
>> +    uint32_t bytes;
>> +    uint32_t cachelen;
>> +    uint32_t cacheval;
>> +} RawBitsEncContext;
>> +
>>  typedef struct OpusRangeCoder {
>>      GetBitContext gb;
>> -    RawBitsContext rb;
>> +    union {
>> +        RawBitsContext rb;
>> +        RawBitsEncContext rbe;
>> +    };
>>      uint32_t range;
>>      uint32_t value;
>>      uint32_t total_bits;
>>
>> and use rbe in ff_opus_rc_put_raw().

> NAK, we don't do anyonymous unions.

The suggested patch does not contain unions.

> To silence the warning the const can be
> just removed,

No, the original data comes from a const pointer.

> but I've never seen a single warning on platforms I've tried.

It is shown on platforms where an optimized function (instead
of the default macro) for AV_RW32() exists, for example Android arm.

Carl Eugen